Cylinders are numbered front to rear. When replacing the distributor have the #1 cylinder at TDC which can be verified by the ball on the flywheel. The wiring in the cap should correspond to the plug wire going to the #1 cylinder. Timing is then set by advancing the distributor by the proper amount to fire BTDC according to the flywheel mark (ball).
Dad probably set it to point at the same place as when he took it out but not realizing the rotation of the rotor due to the spiral cut distributor gear. I'd bet he's off one tooth either short or long so to speak. Or, he could be off 180 degrees. I've seen it done both ways many times.
